A sextant is an astronomical instrument used to determine latitude and longitude at sea by measuring angular distances, especially the altitudes of the sun, moon, and stars. It is a doubly reflecting navigation instrument and used mainly by sailors to measure the angular distance between two visible objects. The name comes from the Latin sextans, or “sixth part of a unit,” because the sextant’s arc can be 60° or 120° of a circle depending on the model used. The primary use was to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation. The estimation of this angle is known as sighting or shooting the object, or taking a sight. This angle and the time when it was measured is used in order to determine Greenwich Mean Time and hence longitude. Sighting the height of a landmark on land can also give a measure of distance from that object. History: The development of the sextant was as an improvement over the octant, an instrument designed to measure one's latitude. The octant was first implemented around 1731-present but can only measure angles up to 45°. As larger angles were needed to allow the measurement of lunar objects - moon, stars and the sun - at higher angles, the octant was superseded by the sextant. The sextant is a similar instrument but better made and allows larger angles from 60° to 120°. This improvement allows distances to be accurately calculated thereby giving longitude when used with a chronometer. The sextant was derived from the octant in 1757, eventually making all previous instruments used for navigational positioning obsolete. The sextant had been attributed to by John Hadley (1682–1744) and Thomas Godfrey (1704–1749), but reference to the sextant was also found later in the unpublished writings of Isaac Newton (1643–1727). Earlier links can be found to Bartholomew Gosnold (1571–1607) indicating that the use of a sextant for nautical navigation predates Hadley's implementation. In 1922, the sextant was modified for aeronautical navigation by Portuguese navigator and naval officer Gago Coutinho. It should be noted that the octant and quadrant are in the same family as they were, and all are, regarded as sextants. The sextant is representative of it's type and although not fully complete it demonstrates how 18th,19th and 20th century mariners determined their latitude and longitudinal to determine their position on a chart, allowing them to navigate there way across the world's oceans. It also demonstrates the skill and workmanship of the early instrument makers that operated scientific instrument businesses from London and other areas of England to provide most of the navigational instrumentation used by commercial and military navies of the time.Sextant with square, fitted box of polished wood, "Hezzanith" brand. Box contains many parts for the sextants use. On certificate "Heath & Co, London. Sextant Number Y 822". Catch on lid "DEFIANT LEVER" and "PATENT NUMBER 187.10". Maker's certificate is attached to the inside of the box.flagstaff hill, warrnambool, shipwrecked-coast, flagstaff-hill, flagstaff-hill-maritime-museum, maritime-museum, shipwreck-coast, flagstaff-hill-maritime-village, sextant box, sextant, hezzanith, heath & co, navigational instrument, george wilson heath, astronomical instrument, instrument manufacturers, scientific instrument, navigation, celestial navigation, octant, quadrant, lunar navigation

This sextant is very similar to a 1915 Sextant design. A sextant is an astronomical instrument used in measuring angular distances especially the altitudes of sun, moon and starts at sea determining latitude and longitude.This sextant is an example of a 19th-century marine instrument used for finding location at sea. It was made by London scientific instrument maker Troughton and Simms, which originated in 1826 and continued until 1922.Sextant and its fitted square wooden box. The handle of the sextant is carved with a cross-hatched pattern. Made by Troughton and Simms, London.flagstaff hill, warrnambool, shipwrecked-coast, flagstaff-hill, flagstaff-hill-maritime-museum, maritime-museum, shipwreck-coast, flagstaff-hill-maritime-village, sextant, navigational instrument, marine navigation, marine equipment, instrument, navigation, troughton and simms, london, scientific instrument

Box with fittings/padding inside for securing sextant (see Item 0172.1)Front Plate: 68/151 BUBBLE SEXTANT MK. IX No. 15708/40 INDEX CORRn. 0

Sextant used by J P Larken, Government Marine SurveyorThe sextant has been the primary position fixing tool of the marine surveyor for 200 years used to measure angles between beacons or points for hydrographic surveys. A sextant in its own wooden box.On inside box lid; 'A. E. Parson surveying and scientific instrument maker, Queen Street, Melbournesextant, jp larken, marine surveyor

Sextant belonging to Walter Harbord (Wal or Wally) (b.1923 in Brisbane-d.), master mariner in the Merchant Navy on British Phosphate Commission ships.Walter was interviewed by the Australian at War Film Archive in 2003. He served on these ships: SS Corinda SS Macumba SS Mildura SS Nellor SS Ormiston SS ReynellaSextant in wooden boxanne rennie collection, wal harbord, merchant navy, seamen, seafarers, ww2, battle of the atlantic, walter harbord, hezzanith, sextant, nautical instrument, navigation

This sextant was used by Captain J Menzies, Harbour Master in Warrnambool who testified in the Victorian Royal Commission of 1925 on the development of Warrnambool Harbour.A maritime instrument with links to Victorian Harbour Development history of the early twentieth century.A brass sextant in wooden box'J Menzies' hand written on box lid.sextant, capt. j. menzies

Sextant belonging to Walter Harbord (Wal or Wally) (b.1923 in Brisbane-d.), master mariner in the Merchant Navy on British Phosphate Commission ships. According to the website SLide Rule Museum this is the Flying Fish 1017 Chemical V2 Walter was interviewed by the Australian at War Film Archive in 2003. He served on these ships: SS Corinda SS Macumba SS Mildura SS Nellor SS Ormiston SS ReynellaSextant in wooden boxInscription in Chinese on the boxanne rennie collection, wal harbord, merchant navy, seamen, seafarers, ww2, battle of the atlantic, walter harbord, nautical instrument, navigation, slide rule, flying fish 1017

Sextant used by Bill Virtue, an apprentice on the Adelaide Steamship Co. ship 'Manoora' in 1957Label on the book indicates that the sextant was examined by the National Physical Museum Kew observatory, Richmond Surrey England in 1901Sextant in timber box made around 1901 in the UK.Examined by National Physical Museum Kew Observatory Richmond Surrey Eng 1901sextant, navigation, 'manoora', adelaide steamship co, bill virtue

A sextant is an instrument generally used to measure the altitude of a celestial object above the horizon. Sextant with a black timber (ebony?) frame, ivory graduated scales and brass attachments : vernier scale radial arm, mirrors and optical filterssextant, astronomy, scientific object, scientific instruments

This item is possibly the sextant donated to the Ballarat School of Mines Museum on 21 October 1885 by D. Turpie of Ballarat.Timber (ebony?) framed sextant with ivory scale, brass radial arm and ivory vernier scale. Mirrors and viewer are set in brass.Maker's label inside the hinged lid.sextant, scientific instrument, d. turpie, navigation, ballarat school of mines museum

Sextantequipment

Sextant on wooden base. Henry Hughes 41598 Caulbrated

Sextant housed in timber box55932

Sextant and wooden box. Wooden quadrant box. Hughes, London

RIDGE PARK, Length: 65.2 m.; Owned by H. Simpson & Sons; Built at S. P. Austin & Sons in 1878. Registered at Adelaide. On 10 February 1881, RIDGE PARK (Capt. Heslop) was on voyage from Adelaide to Sydney with a cargo of brandy, wine and flour, when she was lost after running aground.Beware Reef is located south east of Cape Conran in east Gippsland. This is the sextant from the Ridge Park which, on10 February 1881, was wrecked on Beware Reef , just south of Cape Conran in east Gippsland. An old wooden sextant from the ship, Ridge Park. It is black with yellow measuring stripes.sextant maritime navigational

Metal Box, 5-sided, various sighting and other dials and attachments (including battery compartment)A. M. BUBBLE SEXTANT MARK IX 6B/151 No.15798/40 BRIT. PATS. 480112 490621 AND PENDING

In 1941, the scientific instrument manufacturing firms of  Henry Hughes & Son Ltd, London, England, and  Kelvin Bottomley & Baird Ltd, Glasgow, Scotland, came together to form Kelvin & Hughes Ltd. Kelvin Company History: The origins of the company lie in the highly successful and strictly informal relationship between William Thomson (1824-1907), Professor of Natural Philosophy at Glasgow University from 1846-1899 and James White, a Glasgow optical maker. James White (1824-1884) founded the firm of James White, an optical instrument maker in Glasgow in 1850 and was involved in supplying and mending apparatus for Thomson university laboratory and working with him on experimental constructions. White was declared bankrupt in August 1861 and released several months later. In 1870, White was largely responsible for equipping William Thomson laboratory in the new University premises at Gilmore hill. From 1876, he was producing accurate compasses for metal ships to Thomson design during this period and this became an important part of his business in the last years of his life. He was also involved in the production of sophisticated-sounding machinery that Thomson had designed to address problems encountered laying cables at sea, helping to make possible the first transatlantic cable connection. At the same time, he continued to make a whole range of more conventional instruments such as telescopes, microscopes and surveying equipment. White's association with Thomson continued until he died. After his death, his business continued under the same name, being administered by Matthew Edwards (until 1891 when he left to set up his own company. Thomson who became Sir William Thomson and then Baron Kelvin of Largs in 1892, continued to maintain his interest in the business after James White's death. In 1884 raising most of the capital needed to construct and equip new workshops in Cambridge Street, Glasgow. At these premises, the company continued to make the compass Thomson had designed during the 1870s and to supply it in some quantity, especially to the Admiralty. At the same time, the firm became increasingly involved in the design, production and sale of electrical apparatus. In 1899, Lord Kelvin resigned from his University chair and became, in 1900, a director in the newly formed limited liability company Kelvin & James White Ltd which had acquired the business of James White. At the same time Kelvin's nephew, James Thomson Bottomley (1845-1926), joined the firm. In 1904, a London branch office was opened which by 1915 had become known as Kelvin, White & Hutton Ltd. Kelvin & James White Ltd underwent a further change of name in 1913, becoming Kelvin Bottomley & Baird Ltd. Hughes Company History: Henry Hughes & Sons were founded in 1838 in London as a maker of chronographic and scientific instruments. The firm was incorporated as “Henry Hughes & Sons Ltd” in 1903. In 1923, the company produced its first recording echo sounder and in 1935 a controlling interest in the company was acquired by S Smith & Son Ltd resulting in the development and production of marine and aircraft instruments. Following the London office's destruction in the Blitz of 1941, a collaboration was entered into with Kelvin, Bottomley & Baird Ltd resulting in the establishing “Marine Instruments Ltd”. Following the formal amalgamation of Kelvin, Bottomley & Baird Ltd and Henry Hughes & Sons Ltd in 1947 to form Kelvin & Hughes Ltd. Marine Instruments Ltd then acted as regional agents in the UK for Kelvin & Hughes Ltd who were essentially now a part of Smith's Industries Ltd founded in 1944 and the successors of S. Smith & Son Ltd. Kelvin & Hughes Ltd went on to develop various marine radar and echo sounders supplying the Ministry of Transport, and later the Ministry of Defence. The firm was liquidated in 1966 but the name was continued as Kelvin Hughes, a division of the Smiths Group. In 2002, Kelvin Hughes continues to produce and develop marine instruments for commercial and military. G. Falconer Company History: G Falconer (Hong Kong Ltd) appear to have had a retail presence in Hong Kong since 1885, according to the company website, and currently have a shop in the Peninsula Hotel. G Falconer was the Hong Kong selling agent for several British companies. Ross Ltd of 111 New Bond St London was one and the other was Kelvins Nautical Instruments. Falconers were primarily watchmakers, jewellers and diamond merchants.They were also agents for Admiralty Charts, Ross binoculars and telescopes, and sold English Silverware and High Class English Jewellery. In 1928 the company was operating from the Union Building opposite the Hong Kong general post office. It is unclear if the item is an original Sextant made by Kelvin prior to his amalgamation with Henry Hughes & Sons in 1941 as Kelvin appears to have only made compasses up to this date. If the Sextant can be established that it was made by Kelvin then it is very significant and a rare item made for and distributed through their Hong Kong selling agents G Falconer Ltd. There are many Sextants advertised for sale stating "Kelvin & Hughes 1917 model sextant". These can be regarded as replicas as the company was not formed until 1941 and production of marine instruments was not fully under way until after the war in 1947. Further investigation needs to be undertaken to accurately determine the provenance of this item. As the writer currently has the impression that the subject object was possibly made by Kelvin and Hughes in the mid to late 20th century or is a replica made by an unknown maker in the late 1970s. Purchased as an exhibition of marine navigational instruments for the Flagstaff Hill museum. The Sextant is a brass apparatus with filters and telescope lens, and comes with a wooden felt lined storage box. It is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation.G Falconer and Co. Hong Kong (retailers of nautical equipmentflagstaff hill, warrnambool, shipwrecked-coast, flagstaff-hill, flagstaff-hill-maritime-museum, maritime-museum, shipwreck-coast, flagstaff-hill-maritime-village, sextant, kelvin & hughes ltd, hong kong, navigational instrument, g falconer, mariner's quadrants

Bubble Sextant model Mark 1XA type A.M. 6B/218 in protective storage box. Complete, with operation instructions. This is an aviation navigation instrument used by the RAF and RAAF during the World War 2 era. A sextant is used to measure the altitude of celestial bodies above a horizontal line of reference. A navigator can use the horizon as this line of reference, but when an aircraft is above the clouds or flying at night, the navigator can’t see the horizon. The bubble sextant solves this problem by providing an artificial horizon.The storage case has a label with the following: "A.M. 6B/218 MK IX A" and the number "10772/42 (V)"

An Octant is a doubly reflecting navigation instrument used primarily by sailors to measure the angular distance between two visible objects and was a forerunner of the sextant. The name comes from the Latin octo, or “one-eighth of a circle,” for the Octant’s arc which spans 45°, or one-eighth of a circle. The primary use of an Octant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation. The estimation of this angle is known as sighting or shooting the object, or taking a sight. The angle, and the time when it was measured, can be used to calculate a position line on a nautical chart (latitude), for example, sighting the Sun at noon or Polaris at night (in the Northern Hemisphere) gives an angle by which the latitude can then be estimated. Sighting the height of a landmark on land can also give a measure of distance. History: The principle of the Octant as an instrument to measure ones latitude was first implemented around 1742-present but was superseded by the improvement of the octant to a sextant, a very similar instrument, better made and able to measure bigger angles 120°, allowing the measurement of Luna distances to give longitude when used with an accurate chronometer. The sextant started to appear around 1730 and had been attributed to by John Hadley (1682–1744) and Thomas Godfrey (1704–1749), but reference to the sextant was also found later in the unpublished writings of Isaac Newton (1643–1727). Earlier links can be found to Bartholomew Gosnold (1571–1607) indicating that the use of a Sextant for nautical navigation predates Hadley's implementation. In 1922, the sextant was modified for aeronautical navigation by Portuguese navigator and naval officer Gago Coutinho. Henry Hemsley was a lesser-known instrument maker and optician working in London in the late 17th and early 18th century. However, it should be noted that there were two Henry Hemsley opticians and instrument makers around this period. (Henry Hemsley 1, 1786-89, who had premises at 85 Fleet St London and Henry Hemsley 2, 1828-56), whose workshop was at 135-138 Radcliff Highway London. Therefore, based on the inscribed workshop address Henry Hemsley 2 is responsible for making this example.The octant is representative of its type and although not fully complete it demonstrates how 18th and 19th-century mariners determined their latitude on a chart to navigate their way across the world's oceans in the 18th and 19th century. It also demonstrates the skill and workmanship of the early instrument makers that operated from London at this time and provided most of the navigational instrumentation use by commercial and military navies of the time.Octant, ebony wooden frame and handle. Scale is missing from recess in frame. "H. Hemsley 135-138 Ratliff Highway, London", no box"H. Hemsley 135-138 Ratcliff Highway, London"flagstaff hill, warrnambool, shipwrecked-coast, flagstaff-hill, flagstaff-hill-maritime-museum, maritime-museum, shipwreck-coast, flagstaff-hill-maritime-village, navigation, navigational instrument, instrument used for navigation, sextant, henry hemsley, instrument maker, london, octant

An octant is an astronomical instrument used in measuring the angles of heavenly bodies such as the sun, moon and stars at sea in relation to the horizon. This measurement could then be used to calculate the altitude of the body measured, and then the latitude at sea could also be calculated. The angle of the arms of an octant is 45 degrees, or 1/8 of a circle, which gives the instrument its name. Two men independently developed the octant around 1730: John Hadley (1682–1744), an English mathematician, and Thomas Godfrey (1704–1749), a glazier in Philadelphia. While both have a legitimate and equal claim to the invention, Hadley generally gets the greater share of the credit. This reflects the central role that London and the Royal Society played in the history of scientific instruments in the eighteenth and nineteenth century's. There were also two others who are attributed to having created octanes during this period, Caleb Smith, an English insurance broker with a strong interest in astronomy (in 1734), and Jean-Paul Fouchy, a mathematics professor and astronomer in France (in 1732) In 1767 the first edition of the Nautical Almanac tabulated lunar distances, enabling navigators to find the current time from the angle between the sun and the moon. This angle is sometimes larger than 90°, and thus not possible to measure with an octant. For that reason, Admiral John Campbell, who conducted shipboard experiments with the lunar distance method, suggested a larger instrument and the sextant was developed. From that time onward, the sextant was the instrument that experienced significant development and improvements and was the instrument of choice for naval navigators. The octant continued to be produced well into the 19th century, though it was generally a less accurate and less expensive instrument. The lower price of the octant, including versions without a telescope, made it a practical instrument for ships in the merchant and fishing fleets. One common practice among navigators up to the late nineteenth century was to use both a sextant and an octant. The sextant was used with great care and only for lunar sightings while the octant was used for routine meridional altitude measurements of the sun every day. This protected the very accurate and pricier sextant while using the more affordable octant for general use where it performs well. The invention of the octant was a significant step in providing accuracy of a sailors latitude position at sea and his vessels distance from land when taking sightings of land-based landmarks.Octant with metal handle, three different colored shades are attached, in wooden wedge-shaped box lined with green felt. Key is attached. Two telescope eyepieces are in box. Some parts are missing. Oval ink stamp inside lid of box, scale is graduated to 45 degrees. Ink stamp inside lid of box "SHIPLOVERS SOCIETY OF VICTORIA. LIBRARY"instrument, flagstaff hill, warrnambool, shipwrecked coast, flagstaff hill maritime museum, maritime museum, shipwreck coast, flagstaff hill maritime village, great ocean road, octant, navigation, nautical instrument, navigation instrument, john hadley, sextant, astronomical instrument

Formerly of Station Works, Wakering Road, Barking, Essex, Henry Browne & Son were important British compass makers. The company was founded in the nineteenth century in Barking and London. They were respected English instrument makers who made fine quality compasses, ships clocks, inclinometers, sextants and chandlery items for over 140 years. Their "Dead Beat" compass, which was well dampened to reduce oscillation, was fitted to many Allied ships during the Second World War. Sestrel was their famous Trade Mark brand. The company was sold to John Lilley & Gillie Ltd and SIRS Navigation, both UK companies, in 1993. Example of a hand held compass used in WWIIA Sestrel hand held bearing compass with wooden handle in own glass fronted, wooden container.Sestrel Henry Browne & Son Ltd Barking Londoncompass, navigation

This representative example demonstrates a mariner’s astrolabe. Historical examples are rare. There are less than one hundred known to exist and most of these have been recovered from shipwrecks, many from Spanish and Portuguese vessels. An astrolabe is a measuring device once used to navigate the seas by observing the sun and stars to measure their altitude. The measurement of altitude could then be used to calculate the ship’s latitude but at that time in history there was no means of measuring longitude. The body of the navigational astrolabe was cast brass and much heavier, and less complicated than the variety used on land. The heavier weight and cut-away shape reduced the effect of the wind and waves when trying to use it at sea. A mariner’s astrolabe or ‘star finder’ is a simplified version than that used by Arabic astronomers to find the altitude of the sun and stars above the horizon, and time of the sunrise and sunset. It is a forerunner to the quadrant, octant and sextant and was popular for about 200 years over the 1500s and 1600s to find the latitude of a ship at sea. The user held the astrolabe at eye level and, usually with assistance, aligned the stars through the two small sights (pinnules), then read the altitude indicated by the pointer on the arm. It could also be used to sight the sun by holding it lower down, aiming it at the sun, and adjusting it until the sun shone through both pinnules. This astrolabe is an example used to demonstrate the mariner’s astrolabe, which was navigational tool of the 1500s and 1600s, in the time before longitude was able to be determined. It is a forerunner to modern navigation technology. Mariner’s astrolabe – a representative example. A gold painted, disc shaped object with cut outs and revolving arm in centre. The arm has two sights attached at right angles. The top has a ring attached. Measurements are marked in degrees in a circular scale around outer edge.flagstaff hill, warrnambool, maritime village, maritime museum, flagstaff hill maritime museum & village, shipwreck coast, great ocean road, navigation instrument, navigation tool, navigation, astrolabe, mariner’s astrolabe, measure latitude, measure altitude, arabic navigation, measuring device, star finder, astronomy, marine tool, marine instrument

Henry Browne and Son Ltd, of Barking, made aviation and nautical compasses, clocks and dials. The company made compasses for aircraft notably, Spitfires, Tiger moths and Concord. Henry Browne was born in Lewis, Sussex in 1842 and died in Barking in 1935. His company was a well respected English instrument maker that had been making and selling fine quality compasses, ship's clocks, inclinometers, sextants, and chandlery items for over 140 years. It started in a factory in Brightlingsea, Essex and moved to Barking in 1929. The Trade Mark brand Sestrel was used on all their equipment. Their “Dead Beat“ compass design is well dampened serving to reduce oscillations. It is reported that this design compass was fitted to many Allied ships during WW II. The company went through a boom period in the 1970s but collapsed in the 1980s due to the popularity of cheaper plastic compasses over tradition brass ones. Over more recent years, there has been a consolidation of British instrument makers and the firm of Henry Browne & Son has changed hands a number of times. At last count, it became part of Lillie & Gillie of London in 1985 when John Lilley & Gillie Ltd acquires the assets of Henry Browne & Sons (Sestrel) Ltd, a major competitor for what may be the second time. The model name of Sestral came about via the following.Take first two letters of the word Sensitive then the firs two letter of steady and the firs three letters of reliable hence the trade name of "Sestral". Item relates to the second world war used in many ships of the time merchant and military, It reminds us of a time in our social and world history when most of the world was in conflict.Henry Browne and Sons “Dead Beat“ compass design is well dampened serving to reduce oscillations and was an innervation that many makes of compass of the time din't have as a result the "Sestrel" design was fitted to many Allied ships during WW II.A liquid-filled Sestrel compass, with a brass housing and gimbal ring, wired for an internal low voltage light to illuminate the compass card. Inscriptions printed on face and impressed in metal around outer rim TRADE MARK", "Sestrel Dead-Beat", "No 1724 N", "Barking & London" HENRY BROWNE & SON", additional inscription "AFT No 1724 N". flagstaff hill, warrnambool, shipwrecked-coast, flagstaff-hill, flagstaff-hill-maritime-museum, maritime-museum, shipwreck-coast, flagstaff-hill-maritime-village, compass, marine compass, henry browne & son barking london, sestrel dead-beat marine compass, navigation instrument, sestrel dead-beat marine compass